Actually, there is only a very small amount of steel on a commerical airliner. Most of a plane is made up of thin aluminum for weight saving reasons. The ammunition from those handguns should be capable of piercing aircraft walls. However, none of those handguns have ammunition capable of piercing Kevlar body armor. As for the idea of airline staff carrying firearms for defense, this is an awesome idea! It would really discourage terrorists wouldn't it?

So why are the YTMND fads in the plane, other than so people can say "hey look I know those guys!" of course? "As for the idea of airline staff carrying firearms for defense, this is an awesome idea! It would really discourage terrorists wouldn't it?" Or give terrorists a conveniently accessible firearm? I could understand a lockbox in the cockpit maybe.